I've got the registry set up at the moment. I used facebook and my wedding wire website to let people know.
You can also with the registry print out cards to go in with the save the date or wedding invitations.
Because my wedding is SO small and only 4 months after the engagement ....for me it was the best option for those who wanted to give me something. As although they do take a small fee. I'm moving country after the wedding and so the registry is a lovely setup that lets everyone have a sense of choosing things we enjoy on our wedding/honeymoon without loading me with stuff to move.
Not everyone has chosen to use it but the ones that did loved the idea